DTO pattern for data transfer in Spring Boot - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to declare a simple DTO class with a private field and a getter.

Spring Boot

public class UserDTO {
    private String [1];

    public String getUsername() {
        return username;
    }
}

Drag options to blanks, or click blank then click option'

Ausername

BuserName

Cname

Duser_id

Attempts:

3 left

💡 Hint

Common Mistakes

Using a field name that does not match the getter method name.

Using underscores in field names which is uncommon in Java.

The field name username matches the getter getUsername() following Java naming conventions.

2fill in blank

medium

Complete the code to create a constructor for the DTO that sets the username field.

Spring Boot

public UserDTO([1] username) {
    this.username = username;
}

Drag options to blanks, or click blank then click option'

AUser

BString

Cint

Dboolean

Attempts:

3 left

💡 Hint

Common Mistakes

Using a wrong data type like int or boolean for a username.

Using a complex type like User instead of String.

The username field is a String, so the constructor parameter must be of type String.

3fill in blank

hard

Fix the error in the method that converts an entity to a DTO by filling the blank.

Spring Boot

public static UserDTO fromEntity(User user) {
    return new UserDTO([1]);
}

Drag options to blanks, or click blank then click option'

Auser.getUsername()

Buser.getPassword()

Cuser.getEmail()

Duser.getId()

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the user ID or password instead of username.

Passing a field not present in the DTO constructor.

The DTO expects a username String, so we must pass user.getUsername() from the entity.

4fill in blank

hard

Fill both blanks to complete the DTO class with a setter and override toString method.

Spring Boot

public class UserDTO {
    private String username;

    public void [1](String username) {
        this.username = username;
    }

    @Override
    public String [2]() {
        return "UserDTO{username='" + username + "'}";
    }
}

Drag options to blanks, or click blank then click option'

AsetUsername

BgetUsername

CtoString

DtoStr

Attempts:

3 left

💡 Hint

Common Mistakes

Using getUsername as a setter method name.

Using a wrong method name like toStr instead of toString.

The setter method is named setUsername and the method overriding Object's string representation is toString.

5fill in blank

hard

Fill both blanks to create a method that converts a list of User entities to a list of UserDTOs.

Spring Boot

public static List<UserDTO> fromEntityList(List<User> users) {
    return users.stream()
        .map(user -> new UserDTO([1]))
        .collect(Collectors.[2]());
}

Drag options to blanks, or click blank then click option'

Auser.getUsername()

BtoList

CtoSet

Duser.getId()

Attempts:

3 left

💡 Hint

Common Mistakes

Using user.getId() instead of user.getUsername() in the map.

Using Collectors.toSet() which changes the collection type.

We map each User to a UserDTO by passing user.getUsername(). Then we collect the results into a list using Collectors.toList().